1. Field of the Invention
The present invention relates to a thin film transistor substrate applied to a display device and a fabricating method thereof, and more particularly to a thin film transistor substrate that may be fabricated using a simplified process, and a fabricating method thereof.
2. Discussion of the Related Art
A liquid crystal display device controls light transmittance of a liquid crystal having dielectric anisotropy using an electric field, thereby displaying a picture. The liquid crystal display includes a liquid crystal display panel for displaying a picture through a liquid crystal cell matrix, and a drive circuit for driving the liquid crystal display panel.
Referring to FIG. 1, a liquid crystal display panel of the related art includes a color filter substrate 10 and a thin film transistor substrate 20 that are bonded together with a liquid crystal 24 therebetween.
The color filter substrate 10 includes a black matrix 4, a color filter 6 and a common electrode 8 that are sequentially formed on an upper glass substrate 2. The black matrix 4 is formed on the upper glass substrate 2 in a matrix shape. The black matrix 4 divides areas of the upper glass substrate 2 into a plurality of cell areas where the color filter 6 is to be formed, and prevents a light interference between adjacent cells and an external light reflection. The color filter 6 is formed to be divided into red R, green G, and blue B in the cell areas divided by the black matrix 4 to transmit red, green, and blue light, respectively. The common electrode 8 supplies a common voltage Vcom, that becomes a standard when driving the liquid crystal 24, to a transparent conductive layer that is formed on the entire surface of the color filter 6. In order to level the color filter 6, an overcoat layer (not shown) might be further formed between the color filter 6 and the common electrode 8.
The thin film transistor substrate 20 includes a pixel electrode 22 and a thin film transistor 18 formed in each cell area defined by the crossing of a gate line 14 and a data line 16 on a lower glass substrate 12. The thin film transistor 18 supplies a data signal from the data line 16 to the pixel electrode 22 in response to a gate signal from the gate line 12. The pixel electrode 22 formed of a transparent conductive layer supplies the data signal from the thin film transistor 18, thereby driving a liquid crystal 24.
The liquid crystal having dielectric anisotropy rotates in accordance with an electric field formed by a common voltage Vcom of a common electrode 8 and the data signal of the pixel electrode 22 to control a light transmittance, thereby realizing gray levels.
The liquid crystal display panel further includes a spacer (not shown) to maintain a fixed cell gap between the color filter substrate 10 and the thin film transistor substrate 20.
The color filter substrate 10 and thin film transistor substrate 20 of the liquid crystal display panel are formed by use of a plurality of mask processes. One mask process includes a plurality of processes such as thin film depositing (coating), cleaning, photolithography (hereinafter, referred to as “photo process”), etching, photo-resist stripping, inspecting, etc.
Specially, the thin film transistor substrate includes a semiconductor process and requires a plurality of mask processes, thus its manufacturing process is complicated thus increasing the manufacturing unit price of the liquid crystal display panel. Accordingly, the thin film transistor substrate has been developed to reduce the number of mask processes.